EVIDENCE FOR PLATE TECTONICS

Where is the oldest crust found on the ocean floor?

The oldest crust ever found on the ocean floor is a 3.8 billion old rock formation found in Greenland. Scientists identify the rock as Ophiolites. This rock was created when organisms got caught in the hydrothermal vents which are responsible for seafloor spreading.

Where is the newest crust found on the ocean floor?

The youngest ocean floor is located on mid-ocean ridge. The mid-ocean ridge is located on the eastern side of Europe.

Where do convection currents occur?

Convection currents occur in the geosphere and the atmosphere. They also occur in the hydrosphere. These are all layers of air surrounding the earth.

What do convection currents cause?

Convection currents cause many things on the earth and in the ocean. They cause earthquakes, volcanoes and even cause the plates on the earth to move. The convection currents cause Divergent Boundary , Convergent Boundary and Transformation Faults.

~Divergent Boundary: Where the plates move apart from each other.

~Convergent Boundary: When the plates collide with one another.

~Transformation Faults: Where the plate tectonics slide past each other.

WHAT PROOF DO WE HAVE THAT THE PLATES ON THE EARTH ACTUALLY MOVE?

Jigsaw Fit:

The similar outline of the coastlines of eastern South America and West Africa. The best fit is obtained if the coastlines are matched at a depth of 1,000 meters below current sea level.Any areas where there are gaps or overlaps may be explained by:

Coastal erosion since continental separation

Coastal deposition since continental separation

Rises in sea level (eustatic change) since continental separation

Changes in land level (isostatic change) since continental separation

Geological Fit:

When the geology of eastern South America and West Africa was mapped it revealed that ancient rock outcrops (cratons), over 2,000 million years old, were continuous from one continent to the other.

Glacial Deposits:

A glacial deposit formed during the Permo-Carboniferous glaciation (about 300 million years ago) and is found in Antarctica, Africa, South America, India and Australia. If the continents haven’t moved, then this would suggest an ice sheet extended from the south pole to the equator at this time, but this is unlikely due to the UK being close to the equator.More evidence comes from glacial striations, scratches on the bedrock made by blocks of rock embedded in the ice as the glacier moves. These show the direction of the glacier, and suggest the ice flowed from a single central point.

Fossil Evidence:

There are fossils found on separate continents and nowhere else, suggesting the continents were once joined. If Continental Drift had not occurred, the alternative explanation would be:

The species evolved independently on separate continents , which contradicts Darwin’s theory of evolution.

Paleomagnetism:

Paleomagnetism is the study of the intensity and orientation of the earth's magnetic field found in the magnetic orientation of certain minerals found in rocks formed throughout geologic time. Paleomagnetic studies of rocks and ocean sediment have demonstrated that the orientation of the earth's magnetic field has frequently alternated over geologic time.Paleomagnetic studies of the ocean floor have been of decisive importance in establishing the modern theories of continental drift and seafloor spreading.

Earthquakes:

In the 1950s, at the height of the Cold War, above-ground testing of nuclear weapons was banned under the international treaty.Still each side wanted to know when the other was performing underground nuclear tests,so they started monitoring the movement of the Earth looking for signature shock waves of a nuclear explosion.What they also found was evidence of earthquakes happening continually along certain lines near the boundaries between tectonic plates, which supported Wegners theory

When scientists and geologist started surveying the ocean floor,they found chains of mountains or mid-ocean ridges.From the information gathered scientists now think submarine mountains are created when tectonic plates move apart and magma from the Earth’s mantle moves up to form new oceanic crust.Another way is, on either side of a ridge,a young rock is gradually pushed away in opposite directions and new sea floor forms behind it.With sea floors able to spread like this, the continents connected to them are also pushed around. This explains how continents can move around over time.